In U.S. Pat. No. 4,563,770, Lemelson and Grund disclose an electrical measuring instrument, such as a multimeter, which enables the results of a measurement to be displayed visually as well as by synthesized speech. The meter includes an electrical circuit for the analyzing signals generated in making measurements to assure that no speech report is produced until the signals have stabilized. A foot-operated, normally-open switch permits the operator to trigger the operation of the speech synthesizer when it is desired to generate audible synthetic speech, and also provides the operator with a means for repeating the most recent measurement in the event the operator did not properly hear the previous speech indication of the measurement. While an object of the invention is to enable blind persons to more easily employ the meter due to its speech report, the meter does not solve some of the more troublesome problems with meters with conventional visual displays, much less with speech reporting systems.
Regardless of the means employed for reporting, be it visual or audible, test meters have the nearly universal problem that the operator's hands and vision must usually give attention to the area of the test points. Often it is desired to switch among a plurality of test or report formats; however, there is no provision for such by the device of Lemelson and Grund. For example, where the operator has both hands busy on a complex electrical workpiece and wishes to test resistance followed by voltage and then current, he must remove his test probes from the locale of the test points, manually reset the meter, and again find the test points.
In U.S. Pat. No. 4,604,569, Tedd and Kennedy describe a multimeter having two slide switches on the meter to control test format and an audible alarm to warn of incompatible settings to control test format. Each of the switches is set by the operator to control a different measurement function Where the operator makes a selection of two incompatible setting, a buzzer sounds. While this feature is advantageous, it requires manual setting of the switches and permits the incompatible settings to be made. It would be more desirable to have a meter which could be set from a remote location, e.g., at the location where the operator is using his hands to perform the test of the circuitry, and preferably to include circuitry which would not permit the incompatible test format to be selected and would audibly advise the operator of such by spoken word.
In U.S. Pat. No. 4,633,221, Bradshaw and Evans describe a multimeter including a dual slope analog-to-digital converter having automatic short cycle range determination. The converter adjusts the time period of the signal integrate phase to accommodate different ranges of input signals. Range selection is achieved automatically and rapidly without the need for displaying an out of range reading. While this appears to enhance the utility of typical autoranging meters, it would be desirable to have a meter which, preferably would permit selecting a desired test formal without the operator removing his hands or attention from his workpiece. It would be further desirable to have a meter of this type which would let the operator know in plain English or other language of choice, which test format, in terms of parameters and scale had been selected.
Enabling a meter to report results as synthesized speech is not a full answer to the problems with convenience and efficiency of use. Simply verbalizing reports adds a drawback that, in many cases, much of the information is repetitive and need not be reported. For example, where a long series of tests of one parameter is called for, it is not necessary to report that parameter in all instances and to report all decimal points placements. Often a format, which enabled once reporting the parameter being tested followed by a series of significant digit reports for each test point would not only be adequate, but be desired And, under the circumstances of the present invention, where remote selection of test format, is available, it would be advantageous to enable an audible report of the test format selected.